P. aeruginosa is a Gram-negative aerobic motile bacterium with the form of rods. It is an environmentally ubiquitous, extracellular, opportunistic pathogen that causes significant morbidity and mortality in compromised subjects. Infection is of particular significance in subjects with cystic fibrosis, burns, chronic bronchitis, bronchiectasis and cancer.
Identification of immune responses, the search for vaccine candidates and suitable components for diagnostic tests have focused on components of P. aeruginosa. The outer membrane of P. aeruginosa contains toxins, including the lipopolysaccharide endotoxin, phospholipid and proteins. The various outer membrane proteins (Opr) of P. aeruginosa have been assigned an alphabetical naming system. While several proteins have been characterised by this scheme, the expression of some is only transient and highly dependent upon nutrient availability, culture conditions and the presence of antibiotics. Presently, three major Oprs, designated F,H2 and I, are recognised as antigenically common to and expressed in high copy numbers in all strains of P. aeruginosa. 